Contemporary Epidemiology, Management, and In-Hospital Outcomes of Acute Myocarditis: The Prospective Multicenter MyocarditIRM Study

Abstract

Background: Despite a frequently favorable evolution during the initial phase, acute myocarditis (AM) remains associated with heart failure and ventricular arrhythmia. There are no large prospective databases to provide robust results. Objectives: The aim of this study was to describe baseline characteristics, real-life management, in-hospital outcomes, and determinants of prognosis in a large cohort of patients with AM admitted to cardiology, with a comparison of patients with and without initial severity criteria. Methods: MyocarditIRM (French National Observatory Tracking Viral Myocarditis: Mortality, Cardiovascular Events, Sequels on [Magnetic Resonance Imaging] MRI) is a multicenter prospective observational study of patients with AM confirmed by cardiac magnetic resonance. Patients initially admitted to the intensive care unit or those who died before cardiac magnetic resonance–confirmed diagnosis were not included. Results: In total, 803 consecutive hospitalized patients were enrolled at 49 participating centers between May 2016 and February 2019. The median age was 31 years (Q1-Q3: 23-41 years), and 82% were men. Chest pain was the most frequent symptom (93%), and 112 patients (14%) had severity criteria upon admission (left ventricular ejection fraction <50%, severe ventricular arrythmia, high-degree atrioventricular block, or cardiogenic shock). ST-segment elevation was observed in 49% of patients. Overall, 64 patients (8%) experienced in-hospital complications, defined as a composite of death; left ventricular ejection fraction ≤40%; sustained ventricular or supraventricular arrythmia; cardiogenic shock; and need for mechanical circulatory support, inotropic drugs, temporary cardiac pacing, pacemaker, or cardiac defibrillator implantation. Patients with severity criteria at admission were 10 times more likely to experience in-hospital complications. Conclusions: This prospective cohort represents the largest AM database worldwide. Although the recruitment process likely led to a selection of patients with lower risk AM, 8% experienced in-hospital complications, the major prognosis factor being severity criteria upon admission. (French National Observatory Tracking Viral Myocarditis: Mortality, Cardiovascular Events, Sequels on (Magnetic Resonance Imaging) MRI; NCT02717143)